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In this paper, a novel maximum power point (MPP) tracking technique for photovoltaic system (PV) with fast convergence speed and reduced range for the MPP search operation is presented. The characteristic of this method is the limited searching area/range for the tracking. The adaptable variable duty step used in the proposed method instantaneously brings the operating point close to the MPP, thus bounding the searching area. The value of duty gets updated according to the panel temperature and irradiance, and the operating point always remains close to the MPP. By bounding the search operation, the overall tracking speed and efficiency of the tracking increase. Further enhancement of the tracking speed is obtained by varying the step size of duty ratio of the DC-DC converter used; this is done in such a manner that the size of variable duty step is large for the points far away from MPP and becomes very small at or near MPP. The projected tracking algorithm is compared with conventional Perturb and Observe MPPT method in diverse irradiance and temperature conditions, and evaluation of the proposed tracking method is reported. Finally, field performance of the proposed method has been done by using a 250 W PV system. Arduino Uno microcontroller board is used for controlling the duty of the DC-DC converter. Results obtained from the hardware implementation have been presented and is concluded that the method has fast tracking capability and better efficiency. To sum up, overall performance of the proposed Fast Mutable Duty MPP Tracking technique is appreciable.

A reverse phase-liquid chromatographic method with UV detection at 280 nm is described for simultaneous determination of ceftriaxone sodium and vancomycin hydrochloride. Chromatographic separation of the two drugs was achieved on a Betasil C-1 column using a mobile phase consisting of a binary mixture of acetonitrile and triethylamine buffer adjusted to pH 3.5 ± 0.1 with orthophosphoric acid in a ratio of 20:80. The liquid chromatographic method developed offers symmetric peak shape, good resolution, and reasonable retention time for both drugs. Linearity, accuracy, and precision were found to be acceptable over the concentration ranges 125-750 ppm for ceftriaxone and 62.5-375 ppm for vancomycin. The liquid chromatographic method was successfully applied to the quality control of formulated products, plasma, and cerebrospinal fluid samples containing ceftriaxone and vancomycin.

The multiple power peaks obtained in the power-voltage (P-V) curve of a photovoltaic string under partially shaded condition results in a complicated maximum power point tracking (MPPT) process. Under this condition, the conventional MPPT methods are not acknowledged as they result in false and slow tracking. In this study three novel global MPPT (GMPPT) methods have been proposed and validated. These are named as large and small duty step (LSDS), large and mutable duty step (LMDS) and fast and intelligent GMPPT (FI-GMPPT). The LSDS method sweeps almost the entire P-V curve using a combination of LSDS. Small duty steps are used in predefined areas near all local maximum power points of the P-V curve. LMDS is a further improved method, which uses a combination of LMDSs. The FI-GMPPT is an advance true GMPPT method which limits the area to be swept during the search process. This results in a further reduction in sweep time. In this method, the unnecessary area is skipped during the sweep process. The improved performance of the projected methods has been demonstrated and validated using MATLAB/SIMULINK and hardware implementation.

The paper presents the modeling and performance analysis of a standalone wind system in MATLAB/SIMULINK environment. Stand-alone systems using renewable energy sources, such as wind energy with storage battery banks are commonly used to supply remote houses. The model of wind turbine is developed using basic circuit equations governing the operation of the wind turbine. Permanent Magnet Synchronous Generator (PMSG), which is based on variable-speed operation, has been used in this paper. Since the speed of wind turbine is variable, the generator is controlled by power electronic devices. A rectifier is used to rectify the output voltage of PMSG and DC/DC buck converter is used to decrease this rectified voltage to that of battery and connected DC load. The buck converter is controlled to extract the maximum power output of wind system. Firstly the mathematical modeling of a wind turbine is done and its different characteristics have been obtained for different parameters. Secondly a standalone model of wind system is modeled and analyzed. This paper is useful to model, simulate and study the effect of change in wind speed of a standalone wind system.

Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.007 Å; disorder in main residue; R factor = 0.031; wR factor = 0.088; data-to-parameter ratio = 20.1.

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