Adaptive coordination control strategy of renewable energy sources, hydrogen production unit, and fuel cell for frequency regulation of a hybrid distributed power system

The ‘mismatch losses’ problem is commonly encountered in distributed photovoltaic (PV) power generation systems. It can directly reduce power generation. Hence, PV array reconfiguration techniques have become highly popular to minimize the mismatch losses. In this paper, a dynamical array reconfiguration method for Total-Cross-Ties (TCT) and Series–Parallel (SP) interconnected PV arrays is proposed. The method aims to improve the maximum power output generation of a distributed PV array in different mismatch conditions through a set of inverters and a switching matrix that is controlled by a dynamic and scalable reconfiguration optimization algorithm. The structures of the switching matrix for both TCT-based and SP-based PV arrays are designed to enable flexible alteration of the electrical connections between PV strings and inverters. Also, the proposed reconfiguration solution is scalable, because the size of the switching matrix deployed in the proposed solution is only determined by the numbers of the PV strings and the inverters, and is not related to the number of PV modules in a string. The performance of the proposed method is assessed for PV arrays with both TCT and SP interconnections in different mismatch conditions, including different partial shading and random PV module failure. The average optimization time for TCT and SP interconnected PV arrays is 0.02 and 3 s, respectively. The effectiveness of the proposed dynamical reconfiguration is confirmed, with the average maximum power generation improved by 8.56% for the TCT-based PV array and 6.43% for the SP-based PV array compared to a fixed topology scheme.     

The effect of increasing soaking time on the properties of premixing starch–glycerol–water suspension before melt-blending process: comparative study on the behavior of wheat and corn starches

Polymer Bulletin - The reduction in the torque consumed during the preparation of thermoplastic starch to the minimum value was achieved by reaching equilibrium state of the premixing suspension of...     

High CMRR current-feedback operational amplifier

Despite excellent high frequency and high speed performance, current-feedback operational amplifiers (CFOAs) generally exhibit poor common-mode rejection properties, which limits their utility. In this paper the authors analyse the conventional (CFOA) in terms of common-mode rejection ratio (CMRR) performance, and, having identified the mechanism primarily responsible for the CMRR, they present a modified CFOA input stage circuit design by introducing a combination of a bootstrapping technique and folded cascode transistors. Simulation results of this new CFOA architecture indicate that the amplifier has significantly improved both CMRR and gain accuracy. Other key characteristics are also improved, with the notable exception of slew rate, which is reduced as a consequence of the new topology.     

Determination of Superconducting Parameters of GdBa2Cu3O7?δ Added with Nanosized Ferrite CoFe2O4 from Excess Conductivity Analysis

Superconductor samples of the type (CoFe₂O₄) _x GdBa₂Cu₃O_7??? , 0.0??x??0.1?wt.%, were synthesized by the conventional solid-state reaction technique and were characterized using X-ray powder diffraction (XRD) and scanning electron microscope (SEM). XRD analysis indicated that the orthorhombic structure of Gd-123 is not affected by nanosized ferrite CoFe₂O₄ addition, whereas the volume fraction of Gd-123 increased up to x=0.01?wt.%. Excess conductivity analysis of the investigated samples was analyzed as a function of temperature using the Aslamazov and Larkin (AL) model. It exhibited four different fluctuation regions, namely critical (cr), three-dimensional (3D), two-dimensional (2D), and short-wave (sw). The zero-temperature coherence length along c-axis, effective layer thickness of the two-dimensional system, and inter-layer coupling strength were estimated as functions of nanosized ferrite CoFe₂O₄ concentration. In addition, the thermodynamics, lower and upper critical magnetic fields, and critical current density were calculated from the Ginzburg number. It was found that the low concentration of nanosized ferrite CoFe₂O₄ addition up to x=0.01?wt.% improved the physical properties of Gd-123, while for x>0.01?wt.%, these properties were deteriorated.     

Simplified finite element mesh for dynamic analysis of a nuclear reactor building

The design of nuclear facilities requires dynamic analysis to evaluate their performance during an earthquake. In modal analysis, a method recommended for dynamic analysis by the Nuclear Regulatory Commission, the natural frequencies and mode shapes of the structure are commonly calculated using a stiffness matrix computed using the finite element method. A primary goal of this study was to design a finite element mesh, capable of modelling a reactor structure, with a minimum number of nodes and elements. This is necessary since analysis using a mesh fine enough to include all of the structural elements is not feasible because of exorbitant computer time and storage requirements. It was found that for lateral motion, a representative reactor structure could be accurately modelled using a simplified mesh with only one isoparametric quadratic quadrilateral element per floor. In this mesh essentially infinite springs must be placed between the masses at each floor level to prevent internal movements of the lumped masses within the quadratic quadrilateral elements. It was also found that a structure with rigid heavy bottom floors and a light top floor can be subjected to large displacements in the top floor during earthquakes. It was concluded that the properties of that light top floor (especially shear area) controls the value of the fundamental frequency of the building.