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The inverter is considered the core of the PV power plant. The inverter's failure leads to generation loss and decreases plant availability. So, it is required to investigate a clear Root Cause Analysis (RCA) to deduce the failure causes and implement the required corrective action in addition to the preventive action to avoid more inverter failure, hereby maintaining the plant available to a certain value. This paper discusses real-time mode operation data analysis of the PV grid-connected inverter due to real central inverter incidents in Benban solar park located in Egypt.The central inverter plays an important role in the Mega-Scale PV power plant. The main function of this inverter is to convert the DC power produced by the PV modules to AC power to be injected into the utility grid by considering specific characteristics based on the grid code. The availability of any PV power plant directly depends on the healthy inverter's operation. The more increases for the installed inverters, the less availability loss in the case of inverter partial or catastrophic failures. So, it is required to focus on the failure causes of the central inverter by implementing a technical analysis using the available operational data. The monitored data of the central inverter in the PV power plant is classified into two types. The first type is the continuous time data stored in the memory. It represents the waveforms of inverter outputs like voltage, current, frequency, .... etc. Unfortunately, in case of a catastrophic failure, the central inverter is completely charred, and the continuous time data is lost due to storage memory damage. The second type is the operation data that is recorded by the SCADA system (per one-minute interval). Hereby, the operation data is the sole data in the case of the completely charred inverter. The representation of the operational data in curves indicates symptoms that can be used for the RCA processes. The investigation outcomes include three results. The first result is detecting the signature of the IGBT thermal stress on the voltage balance of the DC link capacitor. The second result is verifying a scenario for the cause of the IGBT failure by implementing a technical mathematical model based on the detected symptoms that denote the fault signature which is considered the thread-tip for detecting the failure cause. The third result is the simulating scenario for the interpretation of a DC link capacitors explosion due to the short circuit fault that occurred due to IGBT failure. The investigation in this paper is performed based on operation data analysis of the PV grid-connected inverter (central type) due to a real incident. The analysis methodology is based on mathematical calculation for the IGBT junction temperature using the measured heatsink temperature. The study concludes that after the IGBT failure occurred, it was a short circuit for a while and closed the terminals of the DC link capacitors. So, the DC link capacitors exploded and produced heavy sparks that led to enough fire to burn the inverter container completely. [ABSTRACT FROM AUTHOR]

The inverter is considered the core of the PV power plant. The inverter's failure leads to generation loss and decreases plant availability. So, it is required to investigate a clear Root Cause Analysis (RCA) to deduce the failure causes and implement the required corrective action in addition to the preventive action to avoid more inverter failure, hereby maintaining the plant available to a certain value. This paper discusses real-time mode operation data analysis of the PV grid-connected inverter due to real central inverter incidents in Benban solar park located in Egypt.The central inverter plays an important role in the Mega-Scale PV power plant. The main function of this inverter is to convert the DC power produced by the PV modules to AC power to be injected into the utility grid by considering specific characteristics based on the grid code. The availability of any PV power plant directly depends on the healthy inverter's operation. The more increases for the installed inverters, the less availability loss in the case of inverter partial or catastrophic failures. So, it is required to focus on the failure causes of the central inverter by implementing a technical analysis using the available operational data. The monitored data of the central inverter in the PV power plant is classified into two types. The first type is the continuous time data stored in the memory. It represents the waveforms of inverter outputs like voltage, current, frequency, .... etc. Unfortunately, in case of a catastrophic failure, the central inverter is completely charred, and the continuous time data is lost due to storage memory damage. The second type is the operation data that is recorded by the SCADA system (per one-minute interval). Hereby, the operation data is the sole data in the case of the completely charred inverter. The representation of the operational data in curves indicates symptoms that can be used for the RCA processes. The investigation outcomes include three results. The first result is detecting the signature of the IGBT thermal stress on the voltage balance of the DC link capacitor. The second result is verifying a scenario for the cause of the IGBT failure by implementing a technical mathematical model based on the detected symptoms that denote the fault signature which is considered the thread-tip for detecting the failure cause. The third result is the simulating scenario for the interpretation of a DC link capacitors explosion due to the short circuit fault that occurred due to IGBT failure. The investigation in this paper is performed based on operation data analysis of the PV grid-connected inverter (central type) due to a real incident. The analysis methodology is based on mathematical calculation for the IGBT junction temperature using the measured heatsink temperature. The study concludes that after the IGBT failure occurred, it was a short circuit for a while and closed the terminals of the DC link capacitors. So, the DC link capacitors exploded and produced heavy sparks that led to enough fire to burn the inverter container completely. [ABSTRACT FROM AUTHOR]

Lung cancer and cutaneous leishmaniasis are critical diseases with a relatively higher incidence in developing countries. In this research, the activity of Carissa macrocarpa leaf hydromethanolic extract and its solvent-fractions (n-hexane, EtOAc, n-butanol, and MeOH) against the lung adenocarcinoma cell line (A549) and Leishmania major was investigated. The MeOH fraction exhibited higher cytotoxic activity (IC50 1.57 ± 0.04 μg/mL) than the standard drug, etoposide (IC50 50.8 ± 3.16 μg/mL). The anti-L. major results revealed strong growth inhibitory effects of the EtOAc fraction against L. major promastigotes (IC50 27.52 ± 0.7 μg/mL) and axenic amastigotes (29.33 ± 4.86% growth inhibition at 100 μg/mL), while the butanol fraction exerted moderate activity against promastigotes (IC50 73.17 ± 1.62), as compared with miltefosine against promastigotes (IC50 6.39 ± 0.29 μg/mL) and sodium stibogluconate against axenic amastigotes (IC50 22.45 ± 2.22 μg/mL). A total of 102 compounds were tentatively identified using UPLC-ESI-MS/MS analysis of the total extract and its fractions. The MeOH fraction was found to contain several flavonoids and flavan-3-ol derivatives with known cytotoxic properties, whereas the EtOAc fractions contained triterpene, hydroxycinnamoyl, sterol, and flavanol derivatives with known antileishmanial activity. Molecular docking of various polyphenolics of the MeOH fraction with HDAC6 and PDK3 enzymes demonstrates high binding affinity of the epicatechin 3-O-β-D-glucopyranoside and catechin-7-O-β-D-glucopyranoside toward HDAC6, and procyanidin C2, procyanidin B5 toward PDK3. These results are promising and encourage the pursuit of preclinical research using C. macrocarpa's MeOH fraction as anti-lung cancer and the EtOAc fraction as an anti-L. major drug candidates. [ABSTRACT FROM AUTHOR]

• The Agavaceae species extracts had promising cytotoxicity against some cancer cells. • Some fractions from P. tuberosa, Y. filamentosa and F. Watsoniana had strong cytotoxicity. • Cytotoxicity shown by extracts may be related to steroidal saponins present. Among the plants which are determined to be a promising source of anticarcenogenic agents are members of Agavaceae family which are common in tropical and subtropical regions such as Egypt. In this study, cytotoxic activity were assessed for the methanolic extracts and fractions from five members of Agavaceae family: Sansevieria cylindrica Bojer., Polianthes tuberosa L., Sansevieria trifasciata Prain., Yucca filamentosa L. and Furcraea watsoniana Hort. against MCF-7 (breast), HepG-2 (hepatoma), and Caco-2 (colon) cancer cell lines by MTT method. The n -hexane fraction of P. tuberosa leaves extract demonstrated strong cytotoxic potential against all three cancer cell lines (CC 50 <20 µg/ml). The ethyl acetate fractions of Y. filamentosa and F. watsoniana leaves significantly inhibited proliferation of hepatocellular HepG-2 (CC 50 = 6.21 µg/ml and 19.07 µg/ml, respectively) and intestinal epithelium Caco-2 carcinoma cells (CC 50 = 18.86 µg/ml and 23.25 µg/ml, respectively). Presumably, the cytotoxic activity exhibited by n -hexane fraction of P. tuberosa , ethyl acetate fractions of Y. filamentosa and F. watsoniana may be related to the steroidal saponins that are present in these samples. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study of Photovoltaic (PV) system performance under desert environmental effects in order to maximize the captured energy of PV system. The proposed study mainly focused on the output power loss of the PV system due to dust accumulation to determine the optimum tilt angle. Eight PV panels were installed on the roof of Faculty of Engineering, Upper Egypt-located in desert environment, at 15°, 20°, 30° and 45° tilt angles with the intention to analyze and compare the performance of the cleaned and dusty solar panels. The output power is recorded for cleaned and dusty solar panels with different tilt angles through the test period. Also, the effect of the panel surface temperature is experimentally studied. The measured data shows that the dust accumulation on the surface of the solar panels reduces the output power. The reduction ratio depends on the number of uncleaned days and tilt angle. The reductions in the output power for dusty panels after ten months of dust accumulation are 43%, 38%, 31%, and 25.5% for tilt angles of 15°, 20°, 30° and 45°, respectively. Also, the optimum tilt angle that gives maximum average output power depends on number of uncleaned days for the dusty panels. On the other hand, the optimum tilt angle for cleaned panels is mainly depends on the season variations. An empirical formula for the output power reduction of the solar panel is proposed and validated to illustrate the correlation between the numbers of dust accumulation days and tilt angle. It helps solar panel system designers to accurately predict the amount of solar power reduction and optimum tilt angle for a specified cleaning schedule. [ABSTRACT FROM AUTHOR]

An ellagitannin monomer, lythracin M (1), and a dimer, lythracin D (2), along with eight known monomers (3 − 10) were isolated from Lawsonia inermis (Lythraceae) leaves. Lythracin M (1) is a C -glycosidic ellagitannin with a flavogallonyl dilactone moiety that participates in the creation of a γ-lactone ring with the anomeric carbon of the glucose core. Lythracin D (2) was determined as an atropisomer of the reported lythcarin D. These newly discovered structures (1 and 2) were determined by intensive spectroscopic experiments and by comparing DFT-calculated 1H 1H coupling, 1H NMR chemical shifts, and ECD data with experimental values. The anti-acetylcholinesterase assay of the compounds 1 – 10 revealed that the C-1 ellagitannin epimers [casuarinin (7 ; IC 50 = 34 ± 2 nM) and stachyurin (8 ; IC 50 = 56 ± 3 nM)], and the new dimer (2 ; IC 50 = 61 ± 4 nM) possess enzyme inhibitory effects comparable to the reference drug (donepezil, IC 50 = 44 ± 3 nM). Molecular docking of compounds 1 – 10 with AChE identified the free galloyl moiety as an important pharmacophore in the anticholinesterase activity of tannins. [Display omitted] • Two new (1 and 2) and eight known ellagitannins (3 – 10) were isolated from leaves of L. inermis. • The stereo-structure of 1 was established based on DFT calculations and intensive spectroscopic studies. • The anti-AChE activity of 1 – 10 was evaluated experimentally and by using molecular docking. • The ellagitannins 2 , 7 , and 8 are promising anti-AChE. [ABSTRACT FROM AUTHOR]

Nowadays, point-of-load (POL) converters’ investments are counted as a main part in power management markets; especially the synchronous buck converters. Today's products forces designers to highly integrate POL converters by increasing the switching frequency; so the latest technology has used megahertz range to obtain this target. On the other hand, increasing switching frequency means increasing the switching losses. Therefore, it is very important to optimize the operating switching frequency tradeoff, which requires an accurate model taking in consideration the converter operating conditions. This paper presents an accurate mathematical loss model taking in consideration the physical behavior of the MOSFET switch in addition to the converter operating conditions. This model introduces accurate equations for every switching intervals and so accurate loss calculations. An integrated POL synchronous buck converter of 5 MHz, 5–1.8 V/3 A prototype is fabricated. The results of the proposed model are compared with simulation and experimental results under variable operating conditions. Good matching between the mathematical, experimental, and simulation results are obtained. [ABSTRACT FROM AUTHOR]

Chromatographic separation of an aqueous acetone extract of the galls from Tamarix aphylla using gels resulted in isolation of an ellagitannin, phyllagallin M1 ( 13 ), a gallo-ellagitannin, phyllagallin D1 ( 14 ), and four gallotannins, phyllagallin M2 ( 15 ) and phyllagallins D2–D4 ( 16 – 18 ), in addition to four known ellagitannins and three phenolics of lower molecular weight structurally related to hydrolyzable tannins. The structures of the six new tannins were elucidated based on spectroscopic and chemical data. Among the phenolics, flavogallonic acid dilactone ( 8 ), which is presumed to be biogenetically produced by C–C oxidative coupling of an ellagic acid unit with a galloyl residue, shows an exceptional oxidative pattern of gallic acid residues in plants of the family Tamaricaceae. Although the ellagitannin tamarixellagic acid ( 4 ) was reported to be a constituent of the galls of T. aphylla , such compounds with anomalous location of the DHDG moiety at O-3 on the glucopyranose core have not been observed among the tannins of tamaricaceous plants. [ABSTRACT FROM AUTHOR]

An on chip integrated power management circuit with maximum power point tracking (PM-MPPT) control is proposed in this paper in order to achieve high efficiency Photovoltaic (PV) system. The proposed PM-MMPT circuit mitigates partial shading issues which exist in PV systems by utilizing cell-level distributed MPPT architecture, where each cell has its own MPPT circuit, in order for each cell to produce its own maximum power without affecting other cells or being affected by other cells. The proposed PM-MPPT circuit consists of two different parts. The first part is a high-efficiency synchronous power converter stage. The second part is an analog ripple correlation control (RCC) MPPT control circuit which provides faster and efficient MPP tracking, has less circuit complexity and low power consumption. HSPICE simulation model of the proposed PM-MPPT circuit is developed with a solar cell that has 0.5 V open circuit voltage and 6 A short circuit current. Simulation results show that the proposed PM-MPPT circuit rapidly tracks the MPP with a tracking efficiency larger than 99% over a wide range of irradiation levels and 92% system power conversion efficiency at a 2 W power level. The detailed analog design of the power stage and the RCC MPPT circuits are presented and discussed in the paper based on 0.35 μm CMOS technology. In addition, the PM-MMPT IC layout is presented and discussed. To validate the proposed technique and design, a comparison between the results of the proposed circuit and other reported techniques from the literature is provided. It is shown that the proposed circuit and system are able to operate with the lowest input voltage and the highest output power compared with other reported techniques. Moreover, the proposed design has the smallest size under 2 W power level. [ABSTRACT FROM AUTHOR]

Licorice, which is the underground part of Glycyrrhiza species, has been used widely in Asian and Western countries as a traditional medicine and as a food additive. Our continuous investigation on the constituents of roots and stolons of Glycyrrhiza uralensis led to the isolation of two new phenolics, in addition to 14 known compounds. Structural studies including spectroscopic and simple chemical derivatizations revealed that both of the new compounds had 2-aryl-3-methylbenzofuran structures. An examination of the effectiveness of licorice phenolics obtained in this study on vancomycin-resistant strains Enterococcus faecium FN-1 and Enterococcus faecalis NCTC12201 revealed that licoricidin showed the most potent antibacterial effects against both of E. faecalis and E. faecium with a minimum inhibitory concentration (MIC) of 1.9 × 10-5 M. 8-(γ,γ-Dimethylallyl)-wighteone, isoangustone A, 3'-(γ,γ-dimethylallyl)-kievitone, glyasperin C, and one of the new 3-methyl-2-phenylbenzofuran named neoglycybenzofuran also showed potent anti-vancomycin-resistant Enterococci effects (MIC 1.9 × 10-5-4.5 × 10-5 M for E. faecium and E. faecalis). The HPLC condition for simultaneous detection of the phenolics in the extract was investigated to assess the quality control of the natural antibacterial resource, and quantitative estimation of several major phenolics in the extract with the established HPLC condition was also performed. The results showed individual contents of 0.08%-0.57% w/w of EtOAc extract for the major phenolics in the materials examined. [ABSTRACT FROM AUTHOR]

The application of plant extracts or plant-derived compounds in the green synthesis of metal nanoparticles (NPs) was researched. Determining the exact metabolite implicated in the formation of NPs would necessitate comprehensive investigations. Copper nanoparticles (CuNPs) are gaining a lot of attention because of their unique properties and effectiveness against a wide range of bacteria and fungi, as well as their potential for usage in catalytic, optical, electrical, and microelectronics applications. In the course of this study, we aimed to formulate CuNPs utilizing pure tamarixinin A (TA) ellagitannin isolated from Tamarix aphylla galls. The main particle size of the formed CuNPs was 44 ± 1.7 nm with zeta potential equal to −23.7 mV, which emphasize the stability of the CuNPs. The X-ray diffraction spectroscopy showed a typical centered cubic crystalline structure phase of copper. Scanning electron microscopy images were found to be relatively spherical and homogeneous in shape. The antimicrobial properties of TA, as well as its mediated CuNPs, have been evaluated through well diffusion assays against four bacterial, Bacillus subtilis NCTC 10400, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853, and two fungal, Candida albicans and Aspergillus flavus, strains. The distinctive antimicrobial activities were noted against the fungal strains and the Gram-negative bacterial strains P. aeruginosa ATCC 27853, and E. coli ATCC 25922. In conclusion, CuNPs mediated by TA can be applied for combating a wide range of bacterial and fungal species especially C. albicans, Asp. flavus, and P. aeruginosa in a variety of fields. [ABSTRACT FROM AUTHOR]

Since our previous study revealed that several licorice phenolics have antibacterial effects on methicillin-resistant Staphylococcus aureus (MRSA), and suppressive effects on the oxacillin resistance of MRSA, we further investigated effectiveness of licorice constituents on vancomycin-resistant Enterococcus (VRE) bacteria, and purified 32 phenolic compounds. Two flavonoids among them were characterized structurally, and identified their structures as demethylglycyrol (31) and 5,7-di-O-methylluteone (32), respectively. Examination of antibacterial effects of licorice phenolics showed that 3-arylcoumarins such as licoarylcoumarin (9) and glycycoumarin (26), and 2-arylcoumarones such as gancaonin I (17), have moderate to potent antibacterial effects on the VRE strains used in this study. [ABSTRACT FROM AUTHOR]

Chemotherapeutic-related toxicity exacerbates the increasing death rate among cancer patients, necessitating greater efforts to find a speedy solution. An in vivo assessment of the protective effect of the C. macrocarpa leaves polar fraction of hydromethanolic extract against doxorubicin (Dox)-induced neurotoxicity was performed. Intriguingly, this fraction ameliorated Dox-induced cognitive dysfunction; reduced serum ROS and brain TNF-α levels, upregulated the brain nerve growth factor (NGF) levels, markedly reduced caspase-3 immunoexpression, and restored the histological architecture of the brain hippocampus. The in vivo study results were corroborated with a UPLC-ESI-MS/MS profiling that revealed the presence of a high percentage of the plant polyphenolics. Molecular modeling of several identified molecules in this fraction demonstrated a strong binding affinity of flavan-3-ol derivatives with TACE enzymes, in agreement with the experimental in vivo neuroprotective activity. In conclusion, the C. macrocarpa leaves polar fraction possesses neuroprotective activity that could have a promising role in ameliorating chemotherapeutic-induced side effects. [ABSTRACT FROM AUTHOR]

In this article, a new single-stage high boosting ratio converter for grid-connected photovoltaic systems is proposed. The proposed system consists of a high voltage gain switched inductor buck-boost inverter that employs a folded cascade H-bridge circuit and operates at line frequency. The proposed system has a single switch operated with a sine wave modulation control. This applied control achieves maximum power point tracking of the input photovoltaic system in addition to the required injected sinusoidal grid current. The proposed system achieves the highest voltage boosting ratio of transformer-less topologies to the authors' best knowledge—more than ten times. In addition, it lowers switching losses and reduces the ground leakage current. A 150-W prototype with input voltage of 20 V and output voltage of 240 V has been developed with the purpose of obtaining experimental results and validating the proposed topology. Results report a boosting voltage gain of about ten times and system efficiency above 85%. [ABSTRACT FROM AUTHOR]

High penetration of renewable energy sources into isolated microgrids (µGs) is considered a critical challenge, as µGs' operation at low inertia results in frequency stability problems. To solve this challenge, virtual inertia control based on an energy storage system is applied to enhance the inertia and damping properties of the µG. On the other hand, utilization of a phase-locked loop (PLL) is indispensable for measuring system frequency; however, its dynamics, such as measurement delay and noise generation, cause extra deterioration of frequency stability. In this paper, to improve µG frequency stability and minimize the impact of PLL dynamics, a new optimal frequency control technique is proposed. A whale optimization algorithm is used to enhance the virtual inertia control loop by optimizing the parameters of the virtual inertia controller with consideration of PLL dynamics and the uncertainties of system inertia. The proposed controller has been validated through comparisons with an optimized virtual inertia PI controller which is tuned utilizing MATLAB internal model control methodology and with H ∞ -based virtual inertia control. The results show the effectiveness of the proposed controller against different operating conditions and system disturbances and uncertainties. [ABSTRACT FROM AUTHOR]

Alternative water sources offer opportunities to contribute to the water supply to meet non-potable urban demand, closing water supply–demand gaps. Detailed assessments of these schemes are often data intensive, which can be a barrier in resource-scarce locations. A data-light approach is proposed and applied to assess the potential contribution of alternative water sources in five cities in the Global South, and to identify barriers preventing their widespread uptake. These barriers include perception, space, cost, home ownership and capacity constraints. This approach is applicable elsewhere, supporting assessment for city water planners/managers for preliminary planning to promote discussion on alternative sources to water security. [ABSTRACT FROM AUTHOR]

Abstract: Shoot cultures of Tamarix tetrandra on Linsmaier–Skoog (LS) agar medium with 30gl−1 sucrose, 2.13mgl−1 indoleacetic acid and 2.25mgl−1 benzyl adenine produced ellagitannins found in intact plants of the Tamaricaceae. This was demonstrated by the isolation of 14 monomeric–tetrameric ellagitannins from the aq. Me2CO extract of the cultured tissues. This is the first report on the production of ellagitannin tetramers by plant tissue culture. The effects of light and certain medium constituents on tissue growth and ellagitannin production were examined. The contents of representative tannins of different types [i.e., tellimagrandin II (monomer), hirtellin A (linear GOG-type dimer), hirtellin B (hellinoyl-type dimer), hirtellin C (macrocyclic-type dimer), and hirtellin T1 (linear GOG-type trimer)] in the resultant tissues in response to these factors were estimated by HPLC, and the optimal condition for production of these tannins were established. Shoots cultured on LS hormone-free medium promoted root development, and regenerated plants could adapt to ordinary soil and climate. Acclimatized and intact T. tetrandra plants that were collected in November and May, respectively, demonstrated seasonal differences in individual ellagitannin contents. HPLC comparison of individual ellagitannin contents in different plant materials (i.e., leaves, stems, and roots) of intact T. tetrandra plants is also reported. The results are discussed with respect to cellular deposition and biosynthetic relationship of tannins. [Copyright &y& Elsevier]

A unified approach for the stability analysis of both preregulator and two-stage power factor correction (PFC) ac–dc converters is presented. Practical and accurate analytical expressions for the stability boundary are obtained by studying the dynamics of the first harmonic component. The resulting model of this dynamics has an equilibrium point at the origin of the harmonic state space. In the case of a stable equilibrium point, the first-order component converges to zero, and the system oscillates at twice the line frequency. If the equilibrium point loses stability, another equilibrium point depending on high-order harmonics will be reached while the real system will exhibit a period-doubling phenomenon leading to subharmonic oscillations. It is demonstrated that the stability boundaries depend on the power level. Numerical simulations and experimental results in both a preregulator and a complete two-stage PFC converter validate the approach. [ABSTRACT FROM PUBLISHER]

Abstract: An ellagitannin monomer, nilotinin M1 (1), and three dimers, nilotinins D1 (2), D2 (3), and D3 (4), were isolated from leaves of Tamarix nilotica (Ehrenb.) Bunge. Structures were elucidated based on analysis of spectroscopic data and chemical correlations with known compounds. In addition, six known tannins, hirtellin A (5) (dimer), remurin A (6), remurin B (7), 1,3-di-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl-β-d-glucose (8), gemin D (9), and hippomanin A (10) (monomers), were isolated for the first time from this plant species. The reported 13C NMR assignments of the dehydrodigalloyl moiety and glucose cores of 5 are revised, and the 13C NMR spectroscopic data for 6 and 7 are also reported for the first time. [Copyright &y& Elsevier]

Boost Power Factor Correction (PFC) AC-DC converter under fixed frequency average current control is a nonlinear and nonautonomous dynamical system characterized by two different forcing periods and thus by two different scales of time. Four different kinds of standard instability phenomena are possible for this system, depending on the parameters of the circuit. A combination of more than one instability phenomenon can also take place. In this paper, we carry out a careful and an accurate modeling of the system. First, we put into evidence most of the nonlinear behaviors that could occur in the system by using the switched circuit-based model and then we derive a unified representative discrete-time model that is able to predict accurately all these behaviors. [ABSTRACT FROM AUTHOR]

Investigation on tannins having antitumor properties led to the isolation of two new C -glycosidic ellagitannins (1 and 2) along with seven known ellagitannins (3 – 9) and a related polyphenolic constituent (10) from Lawsonia inermis leaves. Our intensive HRESIMS, 1D and 2D NMR, and ECD spectroscopic studies of new tannins have shown that one (1) has a monomer structure of C -glycosidic tannin, and the other (2) has a dimeric structure of 2,3- O -hexahydroxydiphenoyl glucopyranose and a C -glycosidic tannin. Among the known compounds, one (3) is a C -glycosidic tannin that was isolated first of all from nature, five were C -glycosidic tannins, vescalagin (4), 1- O -methylvescalagin (5), castalagin (6), stachyurin (7), and casuarinin (8), and one was an O- glycosidic ellagitannin, tellimagrandin II (9). The remaining phenolic constituent from the leaves was identified as valoneic acid dilactone (10). The ellagitannins 1 , and 3 – 9 demonstrated noticeable cytotoxicity on human oral squamous cell carcinoma cell lines (HSC-2, HSC-4, and Ca9–22), and lower effects on human oral normal cells (HGF, HPC, and HPLF). Tellimagrandin II (9) had the highest tumor-specific cytotoxicity, and also cleaved poly (ADP-ribose) polymerase 1 in HSC-2 cells. These findings showed that L. inermis ellagitannins may be a candidate for the production of anti-oral cancer materials. [Display omitted] • Two new (1 and 2), a first isolated from nature (3), and six knowns (4 – 9) ellagitannins, and a related phenolic (10) were isolated from leaves of L. inermis. • The ellagitannins (1 , 3 – 9) exhibited higher cytotoxicity against human oral cancer cell lines (HSC-2, HSC-4, and Ca9–22) than against human normal oral cells (HGF, HPC, and HPLF). • Tellimagrandin II (9) induced cleavage of PARP1 in HSC-2 cells. [ABSTRACT FROM AUTHOR]

The boost power-factor-correction (PFC) converter with average-current-mode control is a nonlinear system due to the effects of the multiplier and a large variation of the duty ratio. Although its stability analysis must be studied depending on a nonlinear model, most prior research attempted to make some assumptions to force this nonlinear system to be linear. As a result, the practical dynamics and the nonlinear phenomena were disregarded. In this paper, two kinds of nonlinear phenomena are detected under the conditions that are considered to be stable by the prior criteria: one is period-doubling bifurcation and the other is chaos. Stability maps and phase-plane trajectories are introduced at different loads to clarify the power factor and also the instability regions. it is clear that the output storage capacitor is a main contributing parameter on the system stability, therefore, bifurcation maps are developed to determine the accurate minimum output capacitance value that assures the system stability under all operating conditions. Also, PFC converter stability is explained and judged by comparing the consequence of charging and discharging energy in the output capacitor. [ABSTRACT FROM AUTHOR]

• Three phase dual-input split-source inverter (DSSI) is proposed for PV systems. • Compared to using one inverter for each PV source, DSSI provides reduced cost and size. • DSSI offers independent and efficient maximum power points tracking. • Experimental and simulation outcomes are presented. This paper presents a dual-input configuration for the three-phase split-source inverter (SSI) to be used with photovoltaic (PV) systems, it is denoted as DSSI. Compared to using one SSI for each PV input, the proposed configuration uses a lower number of semiconductors. Thus, lower cost along with higher power density can be acquired. The proposed DSSI inherits the brilliant features of the conventional SSI. This includes continuity of input current and high voltage boosting gain. The proposed DSSI offers independent control for the power extracted from each PV source. Thus, independent maximum power point (MPP) tracking is ensured. In addition, no circulating current between the input ports is generated. Simple modulation technique is developed for the proposed configuration. In addition, the control system design to ensure independent MPP tracking along with power quality requirements is illustrated. Comparative study with other dual-input topologies is presented. Simulation, experimental as well as real-time simulation results for DSSI are presented. The results show good performance under dual- and single-input scenarios. In addition, well dynamic performance is verified. Thus, performance at steady-state and dynamic conditions is validated for the proposed DSSI. An efficiency of 92.3 % is achieved by the experimental prototype. [ABSTRACT FROM AUTHOR]

The increase in operating temperature of PV generators leads to degradation of their performance. These adverse effects of high temperatures are considered as one of the most important problems that solar panel operation faces in hot weather areas. A lot of research has been undertaken to study this aspect and find ways of limiting the harm caused by such high temperatures. To overcome this harm and to maintain the operating temperature of the PV cells within the optimum range specified by manufacturers, cooling the solar panels often becomes indispensable. This paper discusses the heat transfer through the solar panel layers and studies the effect of high temperature on the solar panel performance in a hot desert environment. It also presents the development of a new solar panel structure viz. by installing an aluminum heat sink to reduce the effect of temperature rise and thus improve the solar panel performance. The study focuses on a pole-mounted solar panel for a street lighting apparatus in extremely hot desert conditions with fluctuating wind speeds. It will be shown that adding an aluminum heat sink to the solar panel bottom mitigates the effect of increased temperature and hence modifies the solar panel operating point by increasing both the efficiency and the lifetime. The solar cell temperature is decreased by 16.4% as a result of the aluminum heat sink installation on the solar panel back sheet and consequently, the accumulated energy produced by the the solar panel is increased by 13.23% per day. [ABSTRACT FROM AUTHOR]

Four flavanolignans, ceibapentains A (1) and B (2) and cinchonains Ia (3) and Ib (4), were isolated for the first time from an ethyl acetate extract of Ceiba pentandra (L) (Bombacaceae) aerial parts. The ceibapentains A (1) and B (2) are new compounds and their structures, including the absolute configurations, were determined by HRESIMS, 1D and 2D NMR, and electronic circular dichroism analyses, then compared with reported data. Compounds 1 – 4 were tested for their anti-Alzheimer's activity via an assessment of their inhibitory effect on amyloid β 42 aggregation using a thioflavin T assay. The results revealed that cinchonain Ia (3) showed a higher inhibitory effect (91%) than the standard curcumin (70%). Compounds 1 , 2 , and 4 exhibited moderate activity, with inhibition ratios of 43%, 47%, and 58%, respectively. A molecular docking study on the binding mode of 3 and curcumin with an amyloid β 1–40 peptide fibril structure indicated a high affinity of cinchonain 1a (3) towards amyloid β 1–40 peptide, in agreement with the experimental results. Unlabelled Image • Isolation of two new and two known flavanolignans from Ceiba pentandra • Investigation of the anti-Alzheimer's activities of the isolated compounds • Assessment of their inhibitory effect on amyloid β 42 aggregation • Molecular docking study on the binding mode of compounds with amyloid β 1–40 [ABSTRACT FROM AUTHOR]

Summary: This paper proposes three‐phase microinverter able to process the power of three PV modules simultaneously and independently; thus, efficient utilization of PV modules through distributed maximum power point tracking (DMPPT) is realized. The proposed microinverter employs switched capacitors (SCs) networks combined with three‐phase voltage source inverter; it is named switched capacitor buck‐boost voltage source inverter and abbreviated as SC‐BBVSI. The connections of SCs networks are determined to fulfill the high boosting gain along with minimized leakage currents. In addition, low capacitances values can be employed for power decoupling purpose. Thus, in addition to DMPPT feature, three features of high boosting gain, high‐reliable product, and minimized leakage current are realized without using the bulky and costly isolation transformer. In this paper, the operation modes of SC‐BBVSI for single and multi‐input scenarios are explained. The modulation strategy to realize these modes along with the control system design is presented as well. The relations required to design the passive elements and identify the device's stresses are derived. The features of the proposed microinverter are confirmed through detailed comparison with other recently reported topologies. Both simulation and experimental results are provided to verify the features of the proposed topology. [ABSTRACT FROM AUTHOR]

AC-DC LED drivers may have a lifespan shorter than the lifespan of LED chips if electrolytic capacitors are used in their construction. Using film capacitors solves this problem but, as their capacitance is considerably lower, the low-frequency ripple will increase. Solving this problem by limiting the output ripple to safe values is possible by distorting the input current using harmonic injection technique, as long as these harmonics still complies with Power Factor Regulations (Energy Star). This harmonic injection alleviates the requirements imposed to the output capacitor in order to limit the low-frequency ripple in the output. This idea is based on the fact that LEDs can be driven by pulsating current with a limited Peak-To-Average Ratio (PTAR) without affecting their performance. By considering the accurate model of LEDs, instead of the typical equivalent resistance, this paper presents an improved and more reliable calculation of the intended harmonic injection. Wherein, its orders and values can be determined for each input/output voltage to obtain the specified PTAR and Power Factor (PF). Also, this harmonic injection can be simply implemented using a single feedback loop, its control circuit has features of wide bandwidth, simple, single-loop and lower cost. A 21W AC-DC buck converter is built to validate the proposed circuit and the derived mathematical model and it complies with IEC61000 3-2 class D standard. [ABSTRACT FROM AUTHOR]

The modulation signal of current source inverter contains an overlap instant to prevent interrupting the dc of the bulky input inductor. This overlap instant, located between vector states, results in output vector deviation errors which, in turn, leads to low-order harmonics in the output waveform. These harmonics are difficult to reject by the output filter. In this article, a novel modulation method is developed to realize zero-vector deviation error and, hence, eliminate the impact of the overlap instant. The ampere–second balance principle is applied to obtain the deviation error expression over the full range of the power factor angle. The mathematical expression of the vector deviation angle is derived in terms of the overlap time. Experimental results are provided to declare the effectiveness of the proposed modulation method. [ABSTRACT FROM AUTHOR]

The micro-inverter has attracted a great deal of attention in PV systems since it offers a superior solution for the shading problem in wide spreading of AC module technology, where each PV module has its own power conditioner. The micro-inverter is implemented from two-stages: DC–DC conversion and DC–AC conversion. This paper focuses on the first-stage of the micro-inverter including its high-gain and maximum power point tracking (MPPT). To achieve these features, an efficient MPPT algorithm is proposed for the LLC resonant-converter. Resonant converters are very promising topologies, due to their inherent features such as high-efficiency and very high-switching-frequency operation. Consequently, they have a small footprint and low switching losses due to zero-voltage-switching (ZVS) operation. To include resonant converters in PV applications, MPPT control is applied. Due to the non-symmetrical operation nature of resonant converters and pulse width modulated converters, the traditional MPPT techniques found in the literature are not suitable for direct application to the resonant converters. They need to be well-tuned before application to a resonant converter. To ease the usage of resonant converters in PV applications, this paper develops a novel phase-shift fixed-frequency MPPT algorithm that is compatible with the LLC resonant converter. It also reduces the EMI when compared to variable-frequency modulation due to the use of ZVS and a fixed frequency. The proposed MPPT technique achieves good performance, high steady-state efficiency and good dynamic response. The complete design procedure and analysis for the proposed MPPT phase-shift algorithm are presented in this paper. Finally, the presented system is validated based on PSIM simulations and hardware implementation on a 300-W prototype. [ABSTRACT FROM AUTHOR]

• Dual-input split-source inverter (DSSI) is proposed for PV systems. • Compared to using one inverter per PV source, DSSI offers lower cost, and size. • DSSI offers independent and efficient maximum power points tracking. • Low capacitance value can be utilized for power decoupling. • Experimental and simulation results are provided to verify the operation of DSSI. This paper proposes dual-input configuration of split-source inverter (abbreviated as DSSI) to transfer the power of two photovoltaic (PV) modules simultaneously or individually. The proposed DSSI keeps the continuity of the input current and the voltage boosting capability offered by the conventional split-source inverter (SSI). Thus, independent as well as efficient tracking of the maximum power points (MPPs) is realized. In addition, low capacitance is utilized for power decoupling in single-phase circuits. Compared to using one SSI per PV source to feed a common load, the proposed DSSI uses lower number of switches at reduced total volt-ampere stresses. Therefore, decreased cost, size, and control circuitry are realized. Simple unipolar modulation technique is presented. Accordingly, the modes of operation and the Volt-ampere stresses of the switches are explained. A closed loop control system is explained to fulfill operation at MPP along with regulation of DC-link voltage and load current. Comparative study with other dual-input topologies is presented. Experimental results as well as real-time simulation results for dual- and single-input scenarios are presented. Also, the dynamic performance under step change in the radiation is investigated. Finally, the capability of operation under different power factors is verified. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper introduces a new configuration of bidirectional multilevel converter in electric vehicle (EV) applications. It has multilevel dc–dc converter with a dc link capacitor voltage balance feature. The multilevel dc–dc converter operates in a bidirectional manner, which is a fundamental requirement in EVs. Compared to the conventional configurations, the proposed one only implements two extra power switches and a capacitor to balance the voltage of the T-type multilevel inverter (MLI) capacitor over a complete drive cycle or at fault conditions. Therefore, no extra isolated sensor, control loops, and/or special switching pattern are required. Moreover, the proposed configuration due to the high-frequency cycle-by-cycle voltage balance between ${C_N}$ and ${C_P}$ , the bulky electrolytic capacitors used in T-type MLI, are replaced with more reliable longer life film capacitors. This will result in a size and weight reduction of the converter by 20%. This allows more real estate for the EV battery in the chassis’ space envelope to increase its capacity. The proposed configuration is tested and validated using a matlab/Simulink simulation model. A laboratory prototype of 1 kW is built to provide the proof of concept results as well. [ABSTRACT FROM AUTHOR]

Purpose: Because of the shortage of energy, the development of green and reliable energy is particularly important. As a green and clean energy, wind power is widely used. As the core component of wind power generation, it is particularly important to choose generators with high reliability. Switched reluctance machine is widely used as generators because of its strong fault tolerance and high reliability. Therefore, this paper aims to propose a power converter and its control strategy to improve the efficiency of switched reluctance generators. Design/methodology/approach: In this paper, a full-bridge power converter (FBPC) instead of the asymmetric half-bridge power converter (AHBPC) is adopted to drive the switched reluctance generator (SRG) system. Compare the FBPC with the AHBPC, the FBPC has several advantages including low cost and modularization, and operation process of SRG winding current direction is variable. Findings: The results show that the SRG system can keep smooth operation by the FBPC with relatively high efficiency. Originality/value: The FBPC is suitable to drive the SRG system. Meanwhile, this paper introduces two excitation modes of the FBPC as three-phase three-beat mode and six-phase six-beat mode. When the six-phase six-beat control strategy is adopted, the dead band time of the converter can be avoided. At the same time, the SRG has higher efficiency. [ABSTRACT FROM AUTHOR]

Aim: The objective of this research is to present a phytochemical profile of Fagonia arabica and to investigate the cytotoxic potential of its extracts against breast, oral, and lung cancer cell lines using MTT assay and dual staining-based mechanistic analysis. Methods: The progressive extraction of F. arabica was carried out using the Soxhlet extraction technique. The total phenolic and flavonoid content was calculated as part of the phytochemical profiling performed using GCMS and LCMS methods. The MTT assay was utilized to assess the cytotoxicity against normal L929 cells, as well as malignant A549, MCF-7, and KB-3-1cell lines. Results: The phenolic compounds and flavonoids were the two main elements of the F. arabica methanolic extract, with 1323 µg GAE/g of dry weight and 523.07 µg QE/g of dry weight, respectively. The presence of the functional phytochemicals was verified by GCMS and LCMS analyses. Toxicity testing on the L929 cell line found that the F. arabica methanol extract was the least harmful, with the highest IC50 (296.11 µg/mL). The MTT assay for cell viability against MCF-7 and KB-3-1 yielded significant results, with IC50 values of 135.02 µg/mL and 195.21 µg/mL, respectively. The aqueous extract exhibited significant cytotoxicity against the A549 cell lines (IC50 116.06 µg/mL). The molecular marker analyses using dual staining revealed that the methanolic extract successfully triggered apoptosis in the different cancer cells tested. Conclusion: The present data suggest that the methanol extract of F. arabica has substantial cytotoxic action against lung, breast, and oral cancer cell lines. Thus, F. Arabica would be a promising source of anticancer medicines, warranting more research to identify the lead molecules with anticancer properties. [ABSTRACT FROM AUTHOR]

The Finite Control Set-Model Predictive Controller (FCS-MPC) for quasi Z-Source Inverters (qZSIs) is designed to reduce the number of sensors by proposing a current observer for the inductor current. Unlike the traditional FCS-MPC algorithm, the proposed model removes the inductor current sensor and observes the inductor current value based on the deposited prior optimized state as well as the capacitor voltage during this state. The proposed observer has been validated versus a typical MPC. Then, a comparative study between the proposed Modified Finite Control Set-Model Predictive Controller (MFCS-MPC) and a linear PID controller is provided under the same operating conditions. This study demonstrates that the dynamic response of the control objectives by MFCS-MPC is faster than that of the PID. On the other hand, the PID controller has a lower Total Harmonic Distortion (THD) when compared to the MFCS-MPC at the same average switching. Experimental results validate both methods using a DSP F28335. [ABSTRACT FROM AUTHOR]

This paper proposes a new three-phase modular multilevel inverter (MMLI). The proposed inverter consists of repeated modular primary cells that are connected in series configuration. Therefore, the proposed topology can be extended to get more output voltage levels by adding additional cells without increasing voltage stresses across power switches. Both sinusoidal pulsewidth modulation (SPWM) and staircase modulation are successfully applied to the proposed inverter. The proposed inverter features many advantages such as reduced number of semiconductor power switches, driver circuits, dc-voltage sources, simplified control algorithm, and reduced voltage stresses across the switches independent of output voltage level. Furthermore, the performance of the proposed inverter is studied under both open-loop and closed-loop operations for highly inductive load. Beside the obtained simulation results, a laboratory prototype has been carried out and tested to verify the control techniques and performances of the topology. Simulation and experimental results are compared together to highlight the similarity and consistence of them. [ABSTRACT FROM AUTHOR]

The objectives of this study are to investigate the cytotoxic effect of different Citrullus colocynthis extracts on breast and lung cancer cell lines using flow cytometry to gain mechanistic insights. C. colocynthis was extracted sequentially using the Soxhlet method. We first tested the plant extracts' cytotoxicity on non-malignant L929 cells and cancerous breast (MCF-7) and lung (A549) cell lines. We observed that the IC50 of the methanol extract on the viability of MCF-7 and A549 cell lines was 81.08 µg/mL and 17.84 µg/mL, respectively, using the MTT assay. The aqueous and methanol extracts were less toxic when tested against the non-cancerous L929 cell line, with IC50 values of 235.48 µg/mL and 222.29 µg/mL, respectively. Then, using flow cytometry, we investigated the underlying molecular pathways with Annexin-V, Anti-Bcl-2, Caspase-3, and DNA fragmentation (TUNEL) assays. Flow cytometric and molecular marker analyses revealed that the methanol extract activated caspase-3 and inhibited Bcl-2 protein, causing early and late apoptosis, as well as cell death via DNA damage in breast and lung cancer cells. These findings indicate that the methanol extract of C. colocynthis is cytotoxic to breast and lung cancer cell lines. The total phenolic and flavonoid content analysis results showed the methanolic extract of C. colocynthis has a concentration of 326.25 μg GAE/g dwt and 274.61 μg QE/g dwt, respectively. GC-MS analysis of the methanol extract revealed phytochemicals relevant to its cytotoxicity. [ABSTRACT FROM AUTHOR]

Osteoporosis, a chronic bone disorder, is one of the leading causes of fracture and morbidity risk. Numerous medicinally important herbs have been evaluated for their efficacy in improving bone mass density in exhaustive preclinical and limited clinical studies. Nigella sativa L. has been used as local folk medicine, and traditional healers have used it to manage various ailments. Its reported beneficial effects include controlling bone and joint diseases. The present manuscript aimed to provide a sound discussion on the pharmacological evidence of N. sativa and its active constituent, thymoquinone, for its utility in the effective management of osteoporosis. N. sativa is reported to possess anti-IL-1 and anti-TNF-α-mediated anti-inflammatory effects, leading to positive effects on bone turnover markers, such as alkaline phosphatase and tartrate-resistant acid phosphatase. It is reported to stimulate bone regeneration by prompting osteoblast proliferation, ossification, and decreasing osteoclast cells. Thymoquinone from N. sativa has exhibited an antioxidant effect on bone tissue by reducing the FeNTA-induced oxidative stress. The present manuscript highlights phytochemistry, pharmacological effect, and the important mechanistic perspective of N. sativa and its active constituents for the management of osteoporosis. Further, it also provides sound discussion on the utilization of a nanotechnology-mediated drug delivery approach as a promising strategy to improve the therapeutic performance of N. sativa and its active constituent, thymoquinone, in the effective management of osteoporosis. [ABSTRACT FROM AUTHOR]

The objectives of this research were to carry out GC–MS and LC–MS-based phytochemical profiling of Barleria hochstetteri, as well as flow cytometry-based mechanistic investigations of the cytotoxic effect of its extracts against breast and lung cancer cell lines. This preclinical in vitro study was carried out in Saudi Arabia and India, from 11 August to 15 January 2022. Barleria hochstetteri was sequentially extracted using the Soxhlet extraction technique. Utilizing LC–MS and GC–MS methods, the phytochemical profiling was performed. Additionally, the total phenolic compounds and flavonoids were quantified in the plant extract using spectrophotometric techniques. In this study, we first examined the cytotoxicity of the plant extract on non-malignant L929 cells and on the carcinogenic MCF-7 and A549 cell lines. Then, we studied the underlying molecular pathways by means of Anti-Bcl-2, caspase-3, and DNA fragmentation (TUNEL) assays, using flow cytometry. The results revealed phenolic compounds and flavonoids to be the two major components in the methanolic extract of B. hochstetteri, with concentrations of 3210 µg GAE/g dwt and 1863 µg QE/g dwt, respectively. Results from GC–MS and LC–MS analyses revealed the presence of bioactive phytochemicals with known cytotoxicity. From the MTT assay on cell viability, the IC50 of the methanol extract for the MCF-7 and A549 cell lines were 219.67 and 144.30 µg/mL, respectively. With IC50 values of 324.24 and 266.66 µg/mL, respectively, the aqueous and methanol extracts were less toxic when tested against the non-cancerous L929 cell line. The extract caused early and late apoptosis in the tested breast and lung cancer cells by activating caspase-3 and inhibiting Bcl-2 protein, and it also caused cell death via DNA damage, based on flow cytometric and molecular marker analyses. These findings indicate that the methanol extract of B. hochstetteri was cytotoxic on breast cancer and lung cancer cell lines. To uncover cancer-fighting chemicals, there is a need for further research on B. hochstetteri, as it is a promising source of anti-cancer chemotherapeutic drugs. [ABSTRACT FROM AUTHOR]

The ethyl acetate and dichloromethane-soluble fractions, from a soft coral Sarcophyton trocheliophorum total methanolic extract, exhibited significant anti-leishmanial and cytotoxic activities. These active fractions yielded a new cembranoid diterpene (1), two known analogues [sarcotrocheliol (2) and sarcophine (3)], and two sterols [(24S)-24-methylcholesterol (4) and gorgosterol (5)]. The structure of the new diterpene (1) was determined via a detailed analysis of its spectroscopic data. Compounds 3 and 5 demonstrated noticeable cytotoxicity on A549 (IC50 17.4 ± 1.9 µg/ml) and HepG2 (IC50 17.7 ± 1.5 µg/ml) cell lines, respectively. None of the isolates 1‒5 showed detectable anti-leishmanial activity (IC50 >100 µg/ml). [ABSTRACT FROM AUTHOR]

A novel method to suppress the force ripple of switched reluctance linear motors (SRLMs) based on predictive-fuzzy control is proposed in this article. Generally, the force ripple mainly occurs in the commutation area, resulting from the dropping force of the outgoing phase that cannot match the rising force of the incoming phase. The force distribution function (FDF) is a suitable method for controlling the forces of the outgoing phase and incoming forces during the commutation area. However, the controller calculation takes time and the motor shows inductive behavior, so the control signal, which is the reference current in FDF, always lags the reference force, which weakens the effect of the FDF control. Considering this problem, a method of predictive-fuzzy control is proposed in this article. The current can be controlled in advance by predicting the force, which reduces the appearance of the negative electromagnetic force, which is beneficial to improving the efficiency of the motor, and the mutual inductance is also considered in the predictive model. Additionally, a fuzzy controller is employed, and adaptive parameters of the control system are adopted. To validate the proposed control system, experimental verification is performed on a 500 W 6/4 double-sided SRLM, showing that the proposed method has a better force ripple suppression performance than the FDF control. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) solar systems with series-connected module integrated converters (MICs) are receiving increased attention because of their ability to create high output voltage while performing local maximum power point tracking (MPPT) control for individual solar panels, which is a solution for partial shading effects in PV systems at panel level. To eliminate the partial shading effects in PV system more effectively, sub-MICs are utilized at the cell level or grouped cell level within a PV solar panel. This study presents the results of a series-output-connection MPPT (SOC-MPPT) controller for sub-MIC architecture using a single sensor at the output and a single digital MPPT controller (sub-MIC SOC-MPPT controller and architecture). The sub-MIC SOC-MPPT controller and architecture are investigated based on boost type sub-MICs. Experimental results under steady-state and transient conditions are presented to verify the performance of the controller and the effectiveness of the architecture. [ABSTRACT FROM AUTHOR]

To reduce the torque ripple of a switched reluctance motor (SRM), this paper proposed a direct torque optimization scheme. To force the torque to better track the reference torque, the proposed method abolished the torque hysteresis control and a fuzzy controller was adopted to quantitatively analyze the difference between the reference torque and measured torque. Therefore, the torque reference factor that represents the torque under different conditions can be obtained, and the system should be controlled by different voltage vectors with different output torque capabilities at different torque reference factor values. In this way, the torque can better track the given torque. At the same time, the existing sectors were optimized in this paper. Under optimized sectors, the adopted direct torque control (DTC) scheme can drive the SRM better. To verify the effectiveness of the proposed scheme, it is compared with the current chop control (CCC) strategy and the traditional DTC control strategy on a 12/8 three-phase SRM by simulations and experiments. The obtained results show that the proposed method can effectively reduce the torque ripple of the SRM. [ABSTRACT FROM AUTHOR]

The paper presents an accurate loss model based controller of an induction motor to calculate the optimal air gap flux. The model includes copper losses, iron losses, harmonic losses, friction and windage losses, and stray losses. These losses are represented as a function of the air gap flux. By using the calculated optimal air gap flux compared with rated flux for speed sensorless indirect vector controlled induction motor, an improvement in motor efficiency is achieved. The motor speed performance is improved using a fuzzy logic speed controller instead of a PI controller. The fuzzy logic speed controller was simulated using the fuzzy control interface block of MATLAB/SIMULINK program. The control algorithm is experimentally tested within a PC under RTAI-Linux. The simulation and experimental results show the improvement in motor efficiency and speed performance. [ABSTRACT FROM AUTHOR]

In this study, a new control of grid-connected doubly-fed induction generators (DFIGs) is introduced to attain lowvoltage ride-through capability. The grid-side converter is proposed to be a multilevel converter (MLC) controlled by conventional DC-link voltage controller. The MLC is designed and integrated into the grid-connected DFIG. The rotor-side converter is considered a two-level conventional converter controlled by the proposed virtual voltage strategy. The virtual strategy is to use the designed input control signal rather than the actual measured one during system disturbance. The system disturbance in this study is the voltage dip. The proposed virtual controller is designed to use busbar voltage during normal operation, whereas it utilizes the designed virtual voltage during wide range conditions of low grid voltages. The energy conversion system currents are increased due to voltage dip disturbances. The use of designed virtual voltage values is proposed as inputs to the controller to limit these currents at the rating values. These virtual voltages are extracted using direct-quadrature machine representation and fixed machine currents at the rated values or lower. On the basis of the proposed control concerning the virtual voltage concept, the generator currents are limited to the rated values, thereby protecting the energy conversion system during low grid voltages. Simulation results prove the validity of the proposed control scheme during extreme low voltages. [ABSTRACT FROM AUTHOR]

Microinverters are an essential part of the photovoltaic (PV) industry with significant exponential prevalence in new PV module architectures. However, electrolyte capacitors used to decouple double line frequency make the single-phase microinverters topologies the slightest unit in this promising industry. Three-phase microinverter topologies are the new trend in this industry because they do not have double-line frequency problems and they do not need the use of electrolyte capacitors. Moreover, these topologies can provide additional features such as four-wire operation. This paper presents a detailed discussion of the strong points of three-phase microinverters compared to single-phase counterparts. The developed topologies of three-phase microinverters are presented and evaluated based on a new classification based on the simplest topologies among dozens of existing inverters. Moreover, the paper considers the required standardized features of PV, grid, and the microinverter topology. These features have been classified as mandatory and essential. Examples of the considered features for classifications are Distributed Maximum Power Point Tracking (DMPPT), voltage boosting gain, and four-wire operation. The developed classification is used to identify the merits and demerits of the classified inverter topologies. Finally, a recommendation is given based on the classified features, chosen inverter topologies, and associated features. [ABSTRACT FROM AUTHOR]

This paper investigates the active damping of grid-connected LCL filter resonance using high-pass filter (HPF) of the grid current. An expression for such HPF is derived in terms of the filter components. This expression facilitates a general study of the actively damped filter behavior in the discrete time domain. Limits for the HPF parameters are derived to avoid the excitation of unstable open loop poles since such excitation can reduce both the damping performance and the system robustness. Based on this study, straightforward co-design steps for the active damping loop along with the fundamental current regulator are proposed. A numerical example along with simulation and experimental results are presented to verify the theoretical analyses. [ABSTRACT FROM AUTHOR]

This paper presents a single-phase five-level inverter controlled by two novel pulse width modulation (PWM) switching techniques. The proposed PWM techniques are designed based on minimum switching power loss and minimum total harmonic distortion (THD). In a single-phase five-level inverter employing six switches, the first proposed PWM technique requires four switches to operate at switching frequency and two other switches to operate at line frequency. The second proposed PWM technique requires only two switches to operate at switching frequency and the rest of the switches to operate at line frequency. Compared with conventional PWM techniques for single-phase five-level inverters, the proposed PWM techniques offer high efficiency and low harmonic components in the output voltage. The validity of the proposed PWM switching techniques in controlling single-phase five-level inverters to regulate load voltage is verified experimentally using a 100 V, 500 W laboratory prototype controlled by dspace 1103. [ABSTRACT FROM AUTHOR]